Electrically controlled multiple character printers



June 7, 1960 ELECTRICALLY CONTROLLED MULTIPLE CHARACTER PRINTERS FiledJuly 19, 1957 J. FROGGATT 4 Sheets-Sheet 1 If CHARACTER- :3 INPUT DRUMCHARACTER STACKING 3. 1e. 17. POSITION CONTROL COUNTER.

V I a 2 p INPUT GATE.

H;;HHL1+ \STYLUS 92 I0. MAGNET ITRIGGIERS. x 8 I a \cIRcuLATINe STATIONREGISTERS. DECODBF SWITCHF 5. 7. a 9 7 I: 13 STYLUS CHARACTERV MAGNETSTATICISERS 11. /TRIGGERS FIG. 1.

CHARACTER STATICISER' oscoome 8 TREE r------------r POSITION I ICOUNTER.

l I I I CHARACTER I2 DRUM. I 61 I I I 2 r l {V I I l I I I48 GATESx1OG6A2TE$ I I J +4 j I l J FIG. 2

.Izaventap BQZFPOfiQ/TJZ June 7, 1960 R. J. FROGGATT 2,939,388

ELECTRICALLY CONTROLLED MULTIPLE CHARACTER PRINTERS Filed July 19, 19574 Sheets-Sheet 2 June 7, 1960 R. J. FROGGATT ELECTRICALLY CONTROLLEDMULTIPLE CHARACTER PRINTERS 4 Sheets-Sheet 3 Filed July 19, 1957 foe 5149 I I l l I l l I CLL\ FIG 40.

June 7, 1960 R. J. FROGGATT 2,939,388

ELECTRICALLY CONTROLLED MULTIPLE CHARACTER PRINTERS Filed July 19, 19574 Sheets-Sheet 4 (d) (e) (f) United States Patent C) ELECTRICALLYCONTROLLED MULTIPLE CHARACTER PRINTERS Robert Justin Froggatt, NorwoodGreen, Southall, England, assignor to Electric & Musical IndustriesLimited, Hayes, England, a company of Great Britain Filed July 19, 1957,Ser. No. 673,023

Claims priority, application Great Britain July 21, 1956 8 Claims. (Cl.101-93) This invention relates to electrically controlled multiplecharacter printers especially though not exclusively to electricallycontrolled line printers.

In data handling apparatus, computing and such like, printing of theoutput information is a matter of some difiiculty, having regard to thespeed at which output information may be generated. One approach to thesolution of this problem is to provide a multiple character printer, forexample, one capable of printing, in each printing cycle a line ofcharacters in the form of dot patterns. Such a line printer for printing140 characters simultaneously in a line may employ 140 styli, one toeach character position along the line, each stylus oscillating in thedirection of the line during the printing of a character as hereinafterdescribed, so that in elfect each stylus scans the respective characterposition in a horizontal line. The movement of the paper is moreoverarranged to provide a scan in a lateral direction to the movement of thestyli. The printing cycle, that is the printing of a line (or character)may be divided into 360 and it is proposed that the printing ofindividual dots be effected by energizing magnets controlling the styliconcerned at any time for 1 only, energization of a magnet causing therespective stylus to move forward and press the paper and a printingmedium into contact, to print a single dot. Thus if the effective pathof the stylus is divided into 360 sections a dot can be printed in anyof these sections, but dots will only be printed where required todelineate the character concerned, by selectively energizing the magnetassociated with said stylus in said 360 sections. However, though such aprinter is capable of operating at a very high speed, the provision 'ofmeans for controlling the energization of the styli magnets which is notunduly complex and costly remains a severe problem, bearing in mind thateach of 140 styli may have to be controlled simultaneously in any one of48 different ways, assuming the printer has an alphabet of 48 characters(including letters and numerals).

The object of the present invention is to provide an economicarrangement for controlling the operation of a line printer, such asdescribed above, for example.

According to the present invention there is provided an electricallycontrolled multiple character printer comprising a plurality of styli, aplaten, means for displacing said styli simultaneously with respect tosaid platen, storage means for storing signals representing charactersto be printed, decoding means, means for cyclically applying saidsignals to said decoding means and means responsive to the outputs ofsaid decoding means for applying energizing signals selectively to saidstyli, the cycle time of said decoding means being short compared withthe description time of a character whereby a multiplicity of energizingsignals may be applied to each stylus during a character descriptiontime.

In order that the invention may be clearly understood and readilycarried into efiect, the invention will be described with reference tothe accompanying drawings in which:

ice

Figure 1 illustrates one example of control mechanism printer operatinggenerally. in the manner above described, and

Figure 2 illustrates in more detail part of Figure 1.

Reference will also be made to the figures of the accompanying drawingsdenoted for convenience by Figures 3 and 4'and in which:

Figure 3 illustrates symbols employed in Figure 4, and

Figure 4, having parts (a), (b), (c) and (d), illustrates a preferredembodiment of a printer according to the present invention.

Reference "1 of Figure 1 indicates an input gate with an input 2 and afurther input from an input stacking control 3. The gate 1 has 14outputs a to a to separate channels, two of which are shown, commencingwith circulating registers 4 and 5 which are connected to characterstaticisers 6 and 7 which are in turn connected to decoders 8 and 9 andthence to station switches 10 and 11, the latter having ten outputswhich are respectively applied to stylus magnet triggers, two of whichare shown in each channel, namely 12, 14 and 13, 15. There is also showna character drum 16 and character position counter 17 which arerespectively connected to the decoders and station switches of eachchannel,

The operation of the example of Figure 1 will be described with the aidof Figure 2 which shows one channel of Figure 1 in more detail andemploys the same references where suitable.

The information required to determine the line of characters to beprinted is derived from a computer in the form of a binary code wherebyeach character is represented by a 6 digit word or coded character, thusallowing for a maximum representation of 64 difierent characters(although only 48 are used in the present case). This information isapplied via input lead 2 to the input gate 1 wherein the information isdirected sequentially, under the control of input stacking controls 3,to fourteen circulating registers such as 4 and 5, one for each outputa, such that each register receives 60 digits, that is 10 words or codedcharacters, which digits are circulated until required. The 10 codedcharacters are applied in turn from each register to characterstaticisers wherein the coded characters are staticised one at a timeand cause 6 signals, in each case, representative of the character to befed to a decoding tree (reference 18, Figure 2) which generates anoutput in one of 48 leads dependent on which character is represented bythe 6 digit word in question. This decoding tree may be of any suitableconstruction, such as described in US. patent specification No.2,682,814, for example. These 48 leads form one set of inputs to 48gates (reference G1, Figure 2) of threshold 2, the other set of inputsbeing derived from the character drum, so that if there are signals inboth inputs to a gate G1 an output pulse is generated in the outputleads of the gate G1. The drum is arranged to have 48 commutators alongits length, each comprising conductive studs angularly disposed aroundthe drum. Each commutator corresponds to a different character and hasits conducting studs positioned to correspond to dots required for thecorresponding character. The drum is rotated once during each printingcycle, that is the printing time of one line of characters or thedescription time of a character, and at such a rate that the 10characters in each register may be staticised before the end of a degreeof rotation of the drum. Thus, in any one degree, ten signals will besequentially applied from the decoding tree 18 to ten of the gates G1and if during this degree there is a conducting stud on any of thecommutators connected to these gates G1 an output from the gate 'orgates G1 will be generated. Each degree of rotation ot the drum 16, issubdivided into ten sections each of six minutes duration (measured interms of said rotation) since the ten characters from the statisciser 6V are applied sequentially to the gates G1. Hence in one degree if a dotis required for each of the ten characters, for example; tenl outputsfrom gates. G1 will be derived sequentiallyvat intervals corres ondingto the time of re;

tation of drum 16 through six minutes. Theteh outputs are appliedsequentially through a common lead, as

shown in Figure 2, to 10 further gates (reference G2, Figure 2) ofthreshold 2 forming a station switch. These gates G2 are operated inconjunction with the character positioncounter 17 which has an inputconnectionto each gateG2 such that the gates G2 may be selectivelyopened so as to direct the sequential outputs from the gates G1 toenergize sequentially appropriate ones of the ten different stylusmagnet -trigger :circuits-,;of which only 12 :and 14 are shown, inaccordance with the order in which they are derived. When all theappropriate triggercircuits in a channel have been energized; that is,after the time of one degree of rotation of drum 16, a pulse from thecharacter position counter is applied to ithe lead .19 (Figure 2) so asto reset the energized trigger circuits, which resetting causes pulsesto be derived from the appropriate end elements B and fire thecorresponding monostable triggers 20 which energize the stylus magnets.It will be noted that the stylus magnets are energized in the degreeafter selection of characters and printing is thus delayed by one degreemeasured in terms of the rotation of the drum 16. c

While printing is' taking place, the stylus magnet triggers,corresponding to those of the 10 characters in the channel whosepatterns necessitate dots in the following degree," are being energized.Clearly, account may' be taken for this 1 delay in printing a dot whenforming the drum commutators. Thepath of'any' one stylus relative to thepaper on which it is required to print will be a zig zag path acrossthat portion of the paper'allocated to one character which the stylusisto print, it being arranged that the speed otvibration of the stylusrelatively to the speed of movement of the paper is sufficiently greatto ensure that each line of the zig zag path is only slightly inclinedto the horizontal. Each zig zag path is efiectively divided into 360sections (related to the 360 of rotation of'the drum 16) in each ofwhich sections a dot can be printed if required for the delineation ofthe character concerned. Each line of the zig zag is arranged to containseveral sections so that if a characterhaving a horizontal limb, such asan E for example, is required to be printed a dot will be printed inmost or all of the sections along one line of the zig zag to delineatethe aforesaid horizontal limb. It will be appreciated that if a dot isprovided in each of the 360 sections an effectively totally black areawill be formed, and that considerably less than 360 dots will berequired for any one character. However it is found that byallocating-360 sections in each of which a dot can, if desired, beprinted any required character can be adequately delineated, andfurthermore conveniently each degree of rotation of the drum 16corresponds to a pos sible dot position. V a

It will be understood that only one channel of fourteen similar channelsis described above with reference to Figure 2, each of said fourteenchannels controlling the printing of 10 characters so that altogether140 characters are printed simultaneously in each line or'during eachso-called printing cycle. Furthermore the ten characters in each of thecirculating registers are continuously sampled by the characterstaticisers duringeach of the 360" of revolution of thedrum16 so thatthe ten signals, representative of ten characters applied to gates G1 inany one channel are repeatedlyapplied thereto, that is once in everydegree of rotation of the drum 16 'until said drum 16 has executeda'complete revolution. After a complete revolution of the drum '16, whenthe complete ten characters in each channel have been printed 4 V V thecirculating registers are cleared, the staticisers are restored to adatum condition and the next 140 characters are fed to the input gate 1.

In an alternative arrangement the 14 circulating registers may bereplaced by a, magnetic drum having one writing head and 14 readingheads, thus affording some economy in apparatus. a a

The embodiment of the present invention just described has the advantagethatin each channel the characters to be printed arederived'sequentially from the staticiser such as 6 and drum 16, thusonly 14 characters are in demand at any time.

Figure 3 illustrates symbols which are employed in Figure.4, whichillustrates a preferred embodiment of the invention, of which symbols:

(a) represents a magnetic core with a 'full strength input winding,

(b) represents a magnetic core with a halfstrength input winding,

(1:) represents a magnetic core with a full strength inhibit winding, 7

(d) represents a magnetic core which is driven by an a pulse and (e)represents a magnetic core with an output winding. Naturally anycombination of the above windings may be used on a single core (f)represents a shunt combination of a registor and a condenser connectedbetween the line and a point of reference potential. The input to thearrangement is via a diode. This circuit is employed as apulselengthening circuit and is more fully described in co-pendingUnited States patent application Serial No. 731,735, filed by G. N.Hounsfield on April 29, 1958. A number of input arrows to the shadedcircle indicates a number of inputs to the circuit via separate diodes.

(g) represents a transistor amplifier operating with grounded emitterand with the output taken from the collector. The drive to thistransistor is limitedsoithat no appreciable hole storage efiect isobtained.

Figure 4(a) illustrates diagrammatically an example of a store which canbe used as a circulating register and staticiser in a printer inaccordance with the invention. The input to the register is via sixleads 21 each of which transmits one binary digit of each character, thesix binary digits of one character being applied to said leads 21simultaneously whilst all characters to be printed in one line areapplied to the leads 21 sequentially during the intervalcorresponding tothe first degree of aprinting cycle. Each binary digit of a character isapplied as a half strength pulse to a core. Thus considering only one ofthe leads, 21, that is the lead labelled 21', the digit in this lead 21is applied to a core 22 as a half strength pulse. A second input in theform of a'half strength pulse is applied to core 22 and eachcorresponding core from input lead 23. The pulses applied through lead23 are denoted by f and consist of a'repeating series of pulses i f fHowever as'will appear from the description of Figure 4c, only oneseries of pulses f f is applied by the lead 23 to the cores 22 of anyparticular register and staticiser during any one printing cycle andnamely during th'efirst degree of that cycle. The core 22, and othercorresponding cores, is driven by pulses f applied via a valve gatingcircuit 31, which consist of a repeating series of pulses f f fe 180 outof phase with respect to pulses f g. Thus after the incidence of a pulsef and a binary digit in lead 21"the core 22 produces an output whendriven by the succeeding f g pulse, which output'is applied at fullstrength to a transistor amplifier 24, one half strength output of which-is laced through each of six cores 25 to 30. The pulses f are alsoapplied sequentially to the cores 25 to '30 via a'valve gating circuit31 so that the half strength output is stored in whichever one of thecores 25 to 30 'is energized with alpulse f It will be appreciated thatcorresponding digits of six consecutive characters will be stored inconsecutive ones of the cores 25 to 30. Thus the digit in lead 21' ofthe first character is stored in core 25, the digit in lead 21' of thesecond character is stored in core 26 and so on for six characters.Likewise the digits of the same six characters in the lead 21 adjacent21' will be stored in the next row of stores corresponding to cores 25to 30, and so on.

The cores 25 to 30 are also driven sequentially by the pulses f viagating circuit 31 so that during the second sequence of pulses i and fthe digits stored in the cores 25 to 30 are sequentially applied via atransistor amplifier 32 to the core 22 at full strength and thence totransistor amplifier 24 after which they are re-stored at half strengthin the same cores 25 to 30 during the pulse intervals f and furtherapplied to the half strength output lead of amplifier 24.

The embodiment of Figure 4 is employed in practice with phase modulateddigit representation so that a 1 is a pulse during the a intervals and a0 is a pulse during the c intervals. Clearly, as so far described, onlythe ls will be temporarily stored in core 22. As a result of this fullstrength f pulses are applied to a further core 33, which core isinhibited whenever a 1 digit pulse is applied from amplifier 32 to core22 and is set to O by the f input pulse in the absence of such aninhibit input. This core 33 is driven by the f pulses as is the core 22to generate a 0 output digit whenever the digit is not a 1 and so noinhibit pulse is applied, said 0 output being in phase with thecorresponding 1 output digit interval. The 0 output pulses are appliedto a transistor amplifier 34, which amplifier produces a half strengthoutput pulse. The remaining five leads of the leads 21 are applied tosimilar core arrangements as that just described so that binary digitsof the first six characters are successively set up in columns of coresand applied to the cores corresponding to 22 and 33 in the similararrangements to be re-stored and fed to the twelve store output leadsdenoted generally by 35, six of which leads are output leads for pulsesrepresenting 0 digits and six of which are output leads for pulsesrepresenting 1 digits. It will be appreciated that in the arrangement ofFigure 4a only six characters are stored in each circulating registerwhereas in the embodiment described with reference to Figures 1 and 2ten characters are stored in each such register. The circuit arrangementof Figure 4a can, of course, readily be designed to accommodate tencharacters at a time if required.

The trigger pulses f and f may be derived in any suitable manner, such,as from the circuit arrangement illustrated in Figure 4(b), forexample. In Figure 4(b) clock pulses T and T derived from the binarycoded character generator, say, are applied to drive alternate ones of aclosed ring of cores having transistor amplifiers intermediate each pairof adjacent cores. In the drawing three consecutive cores, namely 36, 38and 40, are labelled and the two transistor amplifiers connected.therebetween are denoted by references 37 and 39. A double strengthpulse C generated at the beginning of each line of printing, or socalled printing cycle, is applied to the core 36 which is driven by aclock pulse T to inject a pulse into the closed ring. The core 36 is setin a pulse generating condition by Cm, so that when said core is drivenby a clock pulse T it applies an output pulse of short duration equal tothe duration of pulse T to the succeeding amplifier 37 which amplifiersthe output pulse to produce the pulse i and coincidentally apply a fullstrength pulse to the next core 38 to set said core 38 to a pulsegenerating condition. The core 38 is connected to the source of clockpulses T and so is driven when the next pulse T occurs, and caused togenerate an output pulse of duration equal to the duration of T whichoutput pulse is applied to the next amplifier 39 which amplifies saidoutput pulse to produce the pulse 6 f and a fullstrength pulse input tothe following .core 40 to set said core 40 to a pulse generatingcondition whereby a pulse is generated thereby when said core 40 isdriven by the next pulse T and so on around the ring. The pulses T and Tare applied to alternate cores of the ring so that pulses f and f willbe alternately generated, the series of the pulses f being out of phasewith the series of pulses f This process is continued sequentiallyaround the ring the pulses f to i and f to f being repeatedly generatedthe requisite number of times for the characters stored in thecirculating regist ers to be staticised, decoded and applied to controlthe stylus magnet triggers for the printing of the whole of saidcharacters. Thus in the embodiment of the invention described withreference to Figures 1 and 2 it will be appreciated that said charactersare each required to be staticised 360 times, that is once during eachone degree of rotation of the character drum 16. Hence in this examplethe process of generation of pulses f and f will be continued around thering shown in Figure 4b 360 times after which all of the six charactersstored in the stores of Figure 4a will have been printed and arerequired to be cleared so that a further six characters can likewise .bestored during the printing of the next line. Clearing ofthe store iseffected by arresting the application of pulses f and f For this purposethe generation of pulses around the ring of Figure 4b is stoppedby'applying a'further pulse C which acts as a double strength inhibitpulse to all of the cores in the ring except the core 36 which it setsin its pulse generating condition and 'so will cause the cycle to berecommenced at the incidence of the next clock pulse T Figure 4(c)illustrates the preferred embodiment of the invention employing thirteenstores,'or combined circulating registers and character staticisers,such as described with reference to Figure 4(a). The first of thesestores, denoted by reference 41, is employed to store the first sixcharacters in response to inputs from the leads 21 and 23 of Figure4(a), timing pulses i and fi denoted generally by the wire42, and the 0input pulses applied via lead 43.

The decoding of these six characters is achieved by the use of a corematrix 44 having six rows of forty eight cores all of which cores arenormally set to a state termed -1. In operation, the cores of the matrix44 may assume one of three states termed 1, 0 and +1 respectively. Therows are also successively laced, as shown, with leads applying halfstrength pulses f to f and each row of cores is laced by all of thetwelve output wires 35 from the store 41 selectively in such a mannerthat for any particular one of the 48 possible patterns of pulsesappearing at one time in the twelve wires 35, one and only one of thecores in each row receivesa resultant energization equivalent to a halfstrength pulse whereby each core in a row of cores may be considered asrepresenting one character and the cores in each column represent thesame character. This selective lacing is represented in Figlre 4(c) by asingle snaking lead passing through the cores of each row. When thepulses representing a character in six of the twelve wires 35 areapplied to the rows of cores 44 only one core of each row will receive ahalf strength pulse and only one row of cores will have an f pulseapplied thereto at .the time. Hence only one core will be changed instate, the change of the selected core being from 1 to 0. The signalsrepresenting the six characters from the store 41 will be sent insuccession to the matrix of cores 44 their period being, of course,synchronized with the period of the pulses f which are sent insuccession to the six rows of the matrix. Thus each character will causeone core in a different row to be set to 0, that is the first characterwill set the core corresponding thereto in the first row of cores, thesecond character will set the core corresponding thereto in the 7 7 asecond row of cores andso on until one core in each of the six rows isset to 0.{ s 3 a 'Applied to each column of cores 44 is anoutput'leadfroin a character drum 45. i The drum is provided with forty eightcommutators along its length, eachlassociated with one output lead andeach having conducting studsrthereon arranged to represent therelative-positions of the dots required for the character represented bythe. 'matrix column with which that commutator is associated. As thedrum 45 is rotated a pulse is applied-to a column of the cores 44whenever 'a conducting stud comes into line with one of the forty eightoutput leads from said drum 45. If any of the cores in the column towhich such a pulse is applied is already set to by pulses from the leads35 these cores will'be set to 1 by the pulse from the drum andwill thenbe in a condition to generate an output pulse. The rowsof the matrix 44are driven by inputs f f f respectively as shown so that an output pulsefrom a core set to 1 is generated at the incidence of the next f pulseapplied to therow in which the core is located. Thus if a core in 180measured in terms of the period of f and f after such setting and so onfor all rows of the matrix since f g, is 180 delayed relatively to f Itwilbe understood that as in the arrangement of Figure 2 the coresrepresenting thesix characters will be set to 0 duringeach one degree ofrotation of the drum 45 for which purpose the digits of these sixcharacters are fed 360 times to the core matrix 44. However it will beset to 1 onlyfor each degree of the drum in which there is a stud in therespective commutator. a 7 The second group of six characters is appliedto a further store 46 which operates in the same manner as the store 41and has its'twelve outputs connected to a core matrix 47 similar to thematrix 44, and so on for thirteen stores and their matrices. Thesuccessive operation of the stores and thus the setting up of thematrices is achieved by the application of a half strength pulse along awire 23 and corresponding wires for the other stores in successiveperiods defined by a series. of pulses fi For this purpose doublestrength pulse C whichinitiates the circuit of Figure 4(b) is applied toa core 48 which when driven by the f pulses, commencing with pulse fgenerates a half strength output pulse via two parallel transistoramplifiers 49 and 50 and a pulse lengthening circuit 51, this halfstrength output pulse being applied to store 41 along the'wire 23. Thisoutput pulse is also fed back to the core 48 as a full strength inputpulse to set up the core again so that it is driven on the incidence off pulse to generatea second'output, this being continued until an outputpulse is generated in response to the f pulse. The f pulse is alsoapplied to core 48 through a core 52 and via a pulse lengtheningcircuit=53 and transistor amplifier 54 such 'as to' inhibit core 48 whenthe output pulse initiated by f is fed back from the amplifiers 49 and50. The pulse from the amplifier 54 is also applied as a halfstre'ng'thpulseto set up a further core 55. The output along wire 23 isalso applied to core'55 so that this core is set up as a result of pulsef in the first series of f pulses. The core 55 is driven by the f pulsesin the next series, initially h and applies an output pulse to a pulselengthening circuit 56' corresponding to circuit 51 but associated withthe next store '46 whereby a similar sequence of six half strengthpulses is applied to store 46, and so on for the thirteen successivegroups of six characters. The pulse C 'isapplied as a double strengthinhibit to the cores corresponding to 48 of each of these devices otherthan the first so that the printing cycle is stopped on the end of aline. This. pulse C is also applied to inhibit all the cores of thestores. such as that shown in Fig.'4a, t0 resetamplifiers after printingof a line of characters and to condition the apparatus for initiation of.a, new line or printing cycle.

thefirst row is set to 1" an output pulse will be derived It will beappreciated thatithe character's ar'eidecbded cyclically in each corematrix, but it is-arranged that the rate at which each group ofcharacter's'to be printedfin one line is decodedis very much'faster thantheirate of rotation of the character {Conveniently for example, it can'be arranged that the characters to be printed in one lineare decoded atthe rateof 100,000 per second, whilst the drum is rotated at the rate offive revolutions per second. Thus in one dot printing time which is thetime of 1 of rotation of the 'd'rumthech'arac'ters in one line areeffectively simultaneously decodeds- The matrix outputs are applied to alayout switching circuit 57 via amplifiers 58 which are arranged toamplify and integrate the output pulses to form the styli energizatio n'signals required for the character dots. The circuit 57 may be arrangedin any suitable manner to apply; the character outputs to the styli independence upon the particular use of the line printer, which mayinclude predetermined repetition of characters or groups of charactersat the styli. For example if in the printing of output information it isrequired to print two columns of identical characters the dot printingoutputs for these characters will be applied to energize two groups ofstyli, that is each output pulse relating to one character will beapplied simultaneously to energize two different styli. The printerwill, of course, previously be set up so that this or any otherrepetition of characters is efiected. In the arrangement disclosed inFigures 4a, 4b and 40 only 78 character outputs would be produced, butobviously the numbermay be different, for example as in Figures 1 and 2.

Figure 4(d) illustrates the operation of the styli of the printer. Whena dot is required in a particular character position in a line, acontrol pulse is applied tothe appropriate stylus control, which may bea moving coil transducer. By way of illustration five styli controls areshown, denoted by reference 59. Beneath the styli 60 a sheet of carbonpaper is caused to pass from a roller 62, and beneath this carbon papera paper s'heetpasses over a platen 63 immediately below the styli 60.Thus a transducer, when energized by a control pulse, displaces theassociated stylus' 60 downwardly, via a flexible cable connection 61, soas to impress the element of the carbon paper passing immediately belowsaid stylus on to the paper sheet to print a dot on said paper sheet. Asdescribed above, the motion of the paper produces a scanning motion 01relative transverse displacement between the paper and the individualstyli in one direction (perpendicular to a line) and another scanningmotion (along the line) is achieved by oscillating a guide plate 64through which the styli pass. The oscillation may be cam operated asindicated diagrammatically at 65 and is synchronized in response to therotation of magnetic drum store 45 so as to produce a convenient numberof oscillations during the printing time for one line of characters. Ithas been found that 17. is a convenient number of oscillations of thestyli during the printing of one line of characters having regard to thefact that the characters are required to be clearly delineated by meansof dots which may be printed in any of 360 sections of the scanning lineof each stylus over ,a character. Provision must also be made for blankspaces between lines of characters, and this is arranged to occupy aduration equal to a further 5 oscillations of the guide plate 64.Clearly, the rate of the paper feed is also synchronized in response tothat of the drum 45. Furthermoreitwill be understood that the inventionisnot restricted in its applic'ation to multiple character printers inwhich scanning motion between the paper and the styli is achieved partlyby moving the paper and partly by operating the styli. For example insome printers, a plurality of styli are provided arranged across thecharacter positions and are fixed as to their lateral position, andrelative transverse displacement between the paper and the 'styliisproduced solely by movement of the paper. Furthermore the invention isapplicable to other types of printers in which energization of the styliis effected otherwise than by imparting a longitudinal movement to thestyli. For example in some printers energization of styli is achieved byapplying electrical pulses thereto.

Although the invention has been described in relation to line printers,clearly it is not limited thereby and may be applied to any electricallycontrolled printer for printing multiple character lay-outs.

What I claim is:

1. An electrically controlled multiple character printer comprising aplurality of styli, a platen for supporting a medium on which charactersare required to be printed, means for producing relative displacementbetween said styli and said medium simultaneously, storage means forstoring signals representing characters to be printed, decoding means,means for applying said signals to said decoding means in a repetitivecycle, and means responsive to the outputs of said decoding means forapplying energizing signals selectively to said styli, the cycle time ofsaid decoding means being short compared with the description time of acharacter whereby said signals repre senting characters to be printedare applied to said decoding means a plurality of times during acharacter description time.

2. A printer according to claim 1, comprising individual means for eachstylus for moving the respective stylus longitudinally towards saidplaten in response to an energizing signal, the stylus being normallywithdrawn from the platen in the absence of an energizing signal.

3. A printer according to claim 1 wherein said decoding means comprisesa magnetic core matrix.

4. A printer according to claim 1 wherein said storage means comprises astatic magnetic core register.

5. A printer according to claim 1 in which said storage means comprisesa plurality of individual group stores for storing in groups signalsrepresenting characters to be printed in a line, means for sequentiallyapplying to said group stores signals representing characters to beprinted in a line, and said decoding means comprises a character storefor storing representations of a plurality of predetermined characters,and a plurality of decoding elements, one for each group store andincludes means to select bits of character representations from saidcharacter store in response to signals from the respective group store,and temporary stores for storing said bits before energisation of saidstyli.

6. A printer according to claim 5 wherein said character store comprisesa magnetic drum store.

7. An electrically controlled multiple character printer comprising aplurality of styli, one for each character position, a platen forsupporting a medium on which characters are required to be printed,means for producing relative displacement between each stylus and saidmedium simultaneously in two directions to cause each stylus to scan therespective character position, storage means for storing signalsrepresenting characters to be printed, decoding means, means forapplying said signals to said decoding means in a repetitive cycle, andmeans responsive to the outputs of said decoding means for applyingenergizing signals selectively to said styli, the cycle time of saiddecoding means being short compared with the description time of acharacter whereby said signals representing characters to be printed areapplied to said decoding means a plurality of times during a characterdescription time.

8. An electrically controlled multiple character printer comprising aplurality of styli, a platen for supporting a medium on which charactersare required to be printed, means for producing relative displacementbetween said styli and said medium simultaneously, storage means forstoring signals representing characters to be printed, a plurality ofstaticising means each corresponding to a different stylus, decodingmeans associated with said staticising means, means for sequentiallyconditioning said staticising means in response to said storage meansduring a cycle of said decoding means to apply said signals to saiddecoding means in a repetitive cycle, and means for restoring saidstaticising means simultaneously to a datum condition before the nextcycle of said decoding means to produce the energizing signals for saidstyli, the cycle time of said decoding means being. short compared withthe description time of a character whereby said signals representingcharacters to be printed are applied to said decoding means a pluralityof times during a character description time.

References Cited in the file of this patent UNITED STATES PATENTS2,694,362 Paige Nov. 16, 1954

